Abstract: This article explains how my country's synthetic ammonia plants and many coal chemical industries or water treatment industries use structured packing or Applications of random packing. In view of the problems existing in the current application process of structured packing or random packing, this article focuses on the technical characteristics and promotion and application of the independently developed new diversion grid packing.
Keywords: Development of diversion grid packing? Technical characteristics? Application
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1 Question raised
Synthetic ammonia plant in my country As well as many coal chemical industries or water treatment industries, many use packed towers in the process of removing hydrogen sulfide from gas or using circulating water for dust removal and cooling. The packed tower is a traditional gas-liquid contact mass transfer (heat transfer) reaction equipment. The packing is an important component of mass transfer (heat transfer). Its structural design directly affects its mass transfer (heat transfer) efficiency. Ensure long-term stable operation of the equipment.
During the desulfurization or cooling, washing, and dust removal processes, it is inevitable that suspended sulfur, accessory salt crystals, or dust particles and impurities will be deposited on the surface of the packing, gradually causing blockage of the tower equipment and causing gas and liquid in the tower. Uneven distribution, increased resistance, and decreased mass transfer (heat transfer) effect, especially when the packing channels are blocked due to severe siltation in the packing layer, will affect the safe and stable operation of production.
Over the years, the commonly used packings in packed towers include random packings such as Raschig rings, Pall rings, step rings, and saddle rings made of plastic, metal, or ceramics; there are also random packings made of pine wood. The grille filler made of plastic (commonly known as wooden lattice) was later transformed into a grille filler made of plastic in the mid-1980s; there are also corrugated plate fillers made of metal (or plastic), etc. Wooden lattice filler not only involves the source of materials, but also involves the fact that the wood lattice filler is bulky and easily damaged, has a short service life, and requires a complex and lengthy degreasing process for initial use, which affects the rapid and stable operation of the entire production system. and other problems, and were eliminated; the plastic grid packing that was replaced one after another solved the problems of large tower resistance and difficulty in blocking the tower, but due to the specific surface area is much smaller than that of conventional random packing, the gas purification degree is difficult to meet the standard. , and due to structural factors, the structural stability and compressive strength of the filler are poor, and the filler is prone to deformation and collapse, which exposes many problems in actual production and application; although plastic random packing can achieve better mass transfer ( Heat transfer) effect and convenient filling, but due to irregular flow channels, gas and liquid deviation and channeling phenomena are easy to occur. Solids such as suspended sulfur and accessory salts are easy to block in the packing layer, resistance is easy to increase, and cleaning is easy to break , leading to problems such as short production cycles.
2 Comparison of various filler types and development of diversion grid fillers
Chemical fillers are mainly divided into two categories: structured fillers and random fillers.
Structured packing has the advantages of uniform gas-liquid distribution, high mass transfer efficiency (heat transfer), and large production capacity. The usual concept of structured packing is made of metal (stainless steel) sheets or wire mesh through special processing. Although it has high mass transfer (heat transfer) efficiency, due to its compact structure and small porosity, it is generally used in mass transfer (heat transfer) equipment with clean media or chemical towers such as solution distillation and mist separation, and is not suitable It is used in the production of desulfurization, gas dust removal and coking, etc. that are rich in solid suspended solids. Otherwise, solid suspended matter will quickly accumulate in the filler and block the channels, directly affecting the use effect. ?
Structured packing used in the fields of desulfurization, gas dust removal, washing, cooling or water treatment. In the past, there were wooden lattice or bamboo lattice packing, and recently there are plastic grid packing, etc. Due to the regular packing structure, this type of structured packing is easy to select and adjust the form and size of the packing flow channel. It has good gas and liquid flow performance, low resistance, and is not easy to block the tower. However, this type of structured filler has been mentioned above. The wooden grid filler has problems with the source of materials, is heavy and easy to be damaged, and requires long and stubborn degreasing before driving. The plastic grid filler has unreasonable structure, is easy to deform and collapse, and has a small specific surface area. Problems such as difficulty in achieving purification standards.
Random packings are available in various varieties made of metal, plastic or ceramics. They have the characteristics of large specific surface area, simple structure, low cost, and easy loading, unloading and cleaning.
Various types of plastic or metal random packings such as Raschig rings, Pall rings, step rings, and saddle rings are widely used in production fields such as desulfurization and gas dust removal and cooling. There are also ceramic random packings used in higher Gas dust removal, washing, cooling or water treatment fields under temperature conditions. Due to the irregular stacking of random packing, gas and liquid flow disorderly in the packing layer, so it is easy to cause deviation and channeling of gas and liquid. Especially when the solution contains a certain amount of solid matter and suspended matter, it is easy to accumulate in the packing layer and block the packing channels, seriously affecting the mass transfer (heat transfer) efficiency of the packed tower. During the production and operation of random packing, there are problems such as easy increase in resistance, easy flow deviation, easy blockage of the tower, short production cycle, easy breakage during cleaning, etc., and the use effect is not very satisfactory.
In recent years, filler products with various physical and chemical properties have been continuously introduced. There are also many experts and engineering technicians in the industry who are looking for ideal solutions in different ways.
The diversion mesh packing independently developed by our company has been authorized as a national patent and has been used in the desulfurization systems of many units with excellent results and good response. This diversion grid packing is a new type of packing developed based on the specific working conditions of the packed tower and combined with the characteristics of various packings. It has the characteristics of regular packing with good gas and liquid flow performance and low resistance. The vertical flow channel design makes it difficult for suspended matter to accumulate in the packing. It also has the characteristics of a large specific surface area equivalent to that of random packing. Due to the special surface of the packing The design of the flow guide components doubles the specific surface area of ??the filler, which makes the liquid self-distributing ability on the filler surface good, the gas and liquid are evenly distributed, and the mass transfer (heat transfer) efficiency is effectively improved.
3 Basic characteristics of diversion grid packing
The diversion grid packing independently developed by our company can be widely used in gas desulfurization, gas dust removal, washing, cooling or water treatment Field, applied in packed towers with suspended solids, side salt crystallization reaction or media with colloidal properties, dust particles and impurities in the production process, with unique surface guide component design, reasonable specific surface area, and reasonable void ratio , reasonable flow channel and reasonable material are the keys to this packing.
◆The unique design of the guide components of the guide grid filler doubles its specific surface area. The specific surface area is an important parameter of the filler, and it is a key parameter that affects the mass transfer (heat transfer) efficiency. The actual specific surface area utilization of diversion grid packing is higher than that of random packing.
◆? The unique design of the diversion components of the diversion grid filler has the effect of effectively increasing the actual specific surface area utilization of the filler. When the solution flows through the packing layer from top to bottom, countless vertical, dense micro-streams will be generated on both the inner and outer surfaces of the packing, forming a thin and uniform water curtain (liquid film) on the surface of the packing. Good liquid conduction performance and uniform distribution performance enable the gas and liquid phases to be distributed orderly and evenly within the packing layer, which can well avoid the generation of mainstream areas (dead zones) on the packing surface and achieve perfect contact between the gas and liquid phases. , the actual specific surface area utilization of the filler is effectively increased, which is the key to improving the mass transfer (heat transfer) efficiency.
◆ Porosity is an important parameter that affects the ability of gas and liquid phases to pass through the packing layer. The diversion grid packing with special structure has a large void ratio, which can effectively reduce the resistance of the packing layer, reduce the liquid holding capacity of the packing layer, and increase the "liquid flooding" speed of the packing tower.
◆The regular vertical flow channel alleviates the deposition of suspended matter, colloid and other impurities in the packing layer, making it less likely to block the tower, with low tower resistance and long production and operation cycle. The problem of filler clogging is solved through physical methods.
◆? The diversion grid filler is made of polypropylene or reinforced polypropylene and is molded in one step by injection molding. It not only has good structural stability and corrosion resistance, but also has good compressive strength, long service life, light weight, and easy loading and unloading. ?
◆?Due to the actual specific surface area utilization of the diversion grid packing, it can be reduced under the desulfurization conditions where the desulfurization tower production capacity remains unchanged and the packing layer height is the same The circulating amount of desulfurization solution is beneficial to energy saving, consumption reduction and operating cost.
4 Diversion grid packing structure and installation method
4.1 Diversion grid packing structure and assembly
The diversion grid packing is made of polypropylene or Reinforced polypropylene is used as the material, and the block unit structure is made into a block unit structure by injection molding at one time.
According to the diameter of the packed tower, design the processing size of the packing. According to the processing size of the packing, process the unit structure into plates of different styles, number them in sequence according to their shapes, and then assemble them into circles, so as to form each layer of the packing. The specific structure is shown in Figure 1.
4.2 Installation method of diversion grid packing
In order to promote a more perfect contact between the gas and liquid phases in the packing layer, it is conducive to further improving the mass transfer (heat transfer) efficiency , the installation method of the filler is also crucial.
The installation method is: each layer of panels in a combination is stacked at 90° to each other; one combination and another combination are stacked at 45° to each other.
5 Application of diversion grid filler
The main units currently used include:
Water gas desulfurization system of Jiangshan Hydrogen Peroxide Co., Ltd.; Fujian Shaowu Chemical Fertilizer Co., Ltd. Water gas desulfurization system; Hangzhou Longshan Chemical Co., Ltd. semi-water gas desulfurization system; Anhui Jinmei Jinlongyuan Chemical Co., Ltd. (formerly Anhui Feixi Fertilizer Factory, an advanced desulfurization unit) semi-water gas desulfurization system; Anhui Yingshang Xintai Chemical Co., Ltd. semi-water gas desulfurization system Desulfurization system, etc.
6 Conclusions
The diversion grid packing has a large specific surface area, good gas-liquid self-distribution function, high actual effective specific surface area utilization, smooth packing flow channel, and strong anti-blocking performance , The structure is stable and reliable, and it is a structured packing with high efficiency, low resistance, low liquid holding capacity and large flux. It is suitable for gas-liquid phase mass transfer, absorption, washing, cooling and other chemical processes containing suspended solids, accessory salt crystals or dust impurities, such as wet desulfurization, gas washing and purification with large dust content, cooling and other production processes. used in.